1. Field of the Invention
The present invention relates to a gelatino-silver halide photographic emulsion spectrally sensitized by the combination of at least two sensitizing dyes which show a supersensitization action to each other. More particularly, it relates to a silver halide photographic emulsion, particularly for color light-sensistive light-sensitive materials, which has an enhanced spectral sensitivity in the green wave-length region, particularly, at wave-lengths of 500 to 540 nm.
2. Description of the Prior Art
It is known that the sensitivity of the green-sensitive emulsion layer and the spectral distribution thereof greatly influence the color reproducibility of, particularly, color light-sensitive materials (for example, color reproduction of fresh lawn green, discrimination between this lawn green and the dark green of pinetree needles, the degree of fidelity in the color reproduction of objects which are artificially colored green, and the like). Many attempts have been made to improve such color reproducibility. One example thereof is the sensitization of a silver halide emulsion for use in green sensitive layer, which is described in, e.g., Japanese Patent Publication No. 4936/68, 33753/69; U.S. Pat. Nos. 3,397,060, 3,628,964; 3,580/724; 3,617,294; 3,663,210, and 3,666,480. Another example thereof is to enhance the sensitivity of the silver halide emulsion for use in the green sensitive layer in the wave-length region of from 500 to 540 nm. Much effort has been directed to this purpose, which are described in, e.g., U.S. Pat. Nos. 3,617,294 and 3,679,301, German Patent OLS Nos. 2,011,879, and 2,053,187, etc. A further example thereof is to reduce the so-called "remaining of dye" (the stain caused by the dye remaining after development processing) resulting from the sensitizing dye contained in the color light-sensitive materials.
Conventional approaches developed for solving these problems still involve many defects. One of these defects is that where the spectral sensitivity distribution obtained by the supersensitizing combination of an imidazolocarbocyanine dye and a pseudo cyanine dye extends too far in the long wave-length region, it reaches, for example, 580-610 nm, and that the sensitivity at about 545 nm, which is the wave-length of maximum human visual sensitivity and sensitivity in the wave-length region of from 500 to 540 nm are insufficient. When the J-band of the imidazolocarbocyanine dye is partitioned to effect a blue-shift in order to remove this defect as described in, e.g., Japanese Patent Publication No. 1999/71, the sensitivity-inhibiting action by the copresent magenta coupler emulsion is increased. On the other hand, when the peak of J-band is shifted to the short wave-length side by the action of the substituent at the benzimidazole nucleus of the imidazolocarbocyanine dye (e.g., by the introduction of an alkoxycarbonyl group illustrated in the dye described in German Patent Publication No. 2,011,879), the sensitivity-inhibiting action by the copresent magenta coupler emulsion is also increased. Another defect is that pseudocyanine dyes are inherently particularly susceptible to the sensitivity-inhibiting action of the copresent magenta coupler emulsion as compared with other cyanine dyes (this sensitivity-inhibiting action being based on substitution at the 5-position of the benzothiazole or benzoselenazole nucleus of the pseudocyanine), and that copresence of the emulsion thereof increases the remaining of dye. In addition, it is known that, in supersensitization using a pseudocyanine dye, a strict selection of the chemical structure of the pseudocyanine dye is required depending upon the other sensitizing dye combined with the pseudocyanine dye.
In order to remove these defects, the combined use with an oxacarbocyanine dye having a specific chemical structure is employed (which is described in, e.g., German Patent OLS Nos. 2,127,671, 2,135,413, etc.).
An object of the present invention is to remove the above-described various defects. The objects of the invention have been attained by the discovery of a novel system of pseudocyanine dye which causes a much stronger supersensitization particularly with an oxacarbocyanine dye. That is, the desired objects can be attained by incorporating in a silver halide emulsion the combination of at least one sensitizing dye represented by the following general formula (I); ##SPC1##
wherein Z.sub.1 represents a benzothiazole nucleus or benzoselenazole nucleus wherein the carbon atom at the 5-position is substituted by a halogen atom (e.g., a chlorine atom, a bromine atom, etc.), an alkoxycarbonyl group (e.g., a methoxycarbonyl group, an ethoxycarbonyl group, etc.), a cyano group, a trifluoromethyl group or a group having a positive Hammet's constant 6 p (other than a nitro group) (e.g., methylsulfonyl, etc; and acetyl group and a monoaryl group, e.g., phenyl, etc.), such as 5-chlorobenzothiazole, 5-chloro-6-methylbenzothiazole, 5-trifluoromethylbenzothiazole, 5-cyanobenzoselenazole, 5-methoxy-carbonylbenzothiazole, 5-bromo-benzoselenazole, 5-cyano-6-chlorobenzoselenazole nucleus, and the like; Z.sub.2 represents the non-metallic atoms necessary to form a benzene nucleus, thus forming a quinoline nucleus (which can be substituted with substituents such as a lower alkyl group (e.g., methyl, etc.), a halogen atom (e.g. fluorine, bromine, chlorine, etc.), a hydroxy group, a lower alkoxy group (e.g., methoxy, etc.) and a lower alkyl amino group (e.g., methylamino, diethylamino, etc.) such as quinoline, 6-methylquinoline, or the like which is commonly used in pseudocyanine dyes; R.sub.1 and R.sub.2 each represents an aliphatic group including a saturated aliphatic group and an unsaturated aliphatic group for example an alkyl group having 1-6 carbon atoms and a substituted alkyl group (e.g. a lower alkyl group such as a methyl group, an ethyl group, a propyl group; a substituted lower alkyl group, e.g., a phenethyl group, a p-sulfophenethyl group, a sulfopropyl group, a 3-sulfobutyl group, a 4-sulfobutyl group, a 3-sulfo-2-hydroxypropyl group, a 5-sulfo-2-acetoxypentyl group, 2-hydroxy-3-sulfatopropyl group, a 2-carboxyethyl group, a carboxymethyl group, 2-hydroxyethyl group, a 2-cyanoethyl group, a p-carboxyphenethyl group, etc. which are substituted by a sulfo group, a hydroxy group, an acetoxy group, a sulfato group, a carboxy group, an aryl group, a cyano group or the like), at least one of R.sub.1 and R.sub.2 being an lower alkyl group having a sulfo group in either the acid or salt form (e.g., Na, K, etc. salts, amine (e.g. ammonium, triethylamine, etc.) salts; X.sub.1 .sup.- represents an anion necessary to form a cyanine dye salt, such as a mineral acid anion (e.g., an iodide ion, a bromide ion, a perchlorate ion, etc.) and an organic acid anion (e.g., a p-toluene sulfonate ion, a benzenesulfonate ion etc.) m represents 1 or 2 and, when the dye forms an intramolecular salt, m represents 1; and at least one sensitizing dye represented by the following general formula (II); ##SPC2##
wherein V.sub.1 represents a halogen atom (e.g., chlorine atom, a bromine atom, a fluorine atom, etc.), a trifluoromethyl group, a phenyl group, an alkoxycarbonyl group (e.g., in which the alkyl moiety has 1 to 5 carbon atoms e.g., a methoxycarbonyl group, an ethoxycarbonyl group, etc.); V.sub.2 and V.sub.4 each represents a hydrogen atom or a lower alkyl group (e.g., a methyl group, an ethyl group, etc.); V.sub.3 represents a halogen atom, a trifluoromethyl group, a phenyl group, an alkoxycarbonyl group, e.g., in which the alkyl moiety has 1 to 5 carbon atoms, a lower alkyl group (e.g., a methyl group, an ethyl group, etc.), an alkoxy group (e.g., in which the alkyl moiety has 1 to 5 carbon atoms e.g., a methoxy group, an ethoxy group, etc.), a hydroxy group, or a hydrogen atom; at least one V.sub.1, V.sub.2, V.sub.3 or V.sub.4, preferably being substituted by a halogen atom, a phenyl group, or an alkoxycarbonyl group; A represents a methyl group, an ethyl group or a propyl group; R.sub.3 and R.sub.4 each represents the same groups as defined for R.sub.1 and R.sub.2, at least one of R.sub.3 and R.sub.4 being lower alkyl group having a sulfo group or a carboxyl group in either the acid or salt form (e.g., Na, K, etc. salts, amine (e.g., ammonium, triethylanine, etc.) salts; X.sub.2 .sup.- represents the same groups as defined in X.sub.1 .sup.-; n represents 1 or 2 and, when the dye forms an intramolecular salt, n represents 1; with the dyes of the general formulas (I) and (II) being present in such amounts that the combination exhibits a supersensitizing action to each other as used herein, the term lower alkyl is used to described an alkyl group wherein the alkyl moiety has from 1 to 5 carbon atoms.